DE4021899A1 - POLYPROPYLENE MOLDE - Google Patents

Description

The invention relates to a high impact toughness Polypropylene molding compound from a syndiotactic Propylene polymer or a syndiotactic propylene copolymer and an ethylene-propylene copolymer rubber.

Soft polypropylene molding compounds are known in principle. They are made by melt blending isotactic polypropylene (IPP) with a rubber, for example ethylene-propylene rubber (EPM) or Ethylene propylene diene rubber (EPDM). To low Achieving degrees of hardness are uneconomically high Amounts of rubber required.

It is also known isotactic polypropylene, atactic polypropylene (APP) and a rubber too Mix.

However, adding APP leads to sticky products. The APP's low melting point Processing problems and poor heat resistance and from the normally low melt viscosity of the APP results in inhomogeneous products when melt mixing. The use of kneaders when mixing improves the Homogeneity, but at the same time it decreases Economy of the production of the molding compound. About that APP also works when its glass temperature falls below no longer as a plasticizer in the molding compound, but leads contrary to embrittlement.

The task was to create a soft polypropylene molding compound to find the one that has high impact strength and Possesses flexibility even at very low temperatures and on the other hand is economical to manufacture.  

The task could be solved by using a syndiotactic propylene polymer instead of isotactic polypropylene and melt blending with one Rubber.

The invention thus relates to a polypropylene molding composition, consisting essentially of 20 to 99 wt .-%, based on the molding compound, a syndiotactic propylene polymer and 1 to 80 wt .-%, based on the molding compound, one Rubber with a glass transition temperature below -30 ° C.

The for the production of the polypropylene molding composition according to the invention syndiotactic propylene polymer to be used is a polymer in which part of the Molecular chains the same every other tertiary carbon atom Configuration.

The propylene polymer is either a propylene homopolymer with a syndiotaxy index of at least 75% or one or two propylene copolymers with one syndiotactic Index of at least 75%.

If the propylene polymer is only a single propylene copolymer, it consists of 99.5 to 50, preferably 99 to 70% by weight propylene units with a syndiotaxy index of at least 75% and 0.1 to 50, preferably 1 to 30% by weight .-% units of ethylene or an olefin having at least 4 carbon atoms of the formula Ra-CH = CH-R ^b , in which Ra and R ^{b are} identical or different and a hydrogen atom or an alkyl radical having 1 to 10, preferably to C- Atoms mean or Ra and R ^{b form} a ring with 4 to 22 C atoms with the C atoms connecting them. Preferred comonomers are ethylene, butene-1, 4-methyl-1-pentene, hexene-1, norbornene and pentene.

If the propylene polymer consists of two propylene copolymers is a copolymer (a) of 95 to 100,  preferably 98 to 100 wt .-% propylene units with one Syndiotaxy index of at least 75% and 0 to 5, preferably 0 to 2% by weight of units of ethylene or an olefin as defined above, and that others a copolymer (b) of 20 to 90, preferably 40 up to 90% by weight propylene units with a syndiotaxy index of at least 75% and 10 to 80, preferably 10 to 60% by weight Units of ethylene or an olefin as is is defined above. The share of the two Copolymers (a) and (b) in the propylene polymer is 20 to 99, preferably 40 to 95 wt .-% copolymer (a) and 1 to 80, preferably 5 to 60% by weight of copolymer (b), each based on the amount of propylene polymer.

The syndiotactic propylene polymer is in the Molding composition according to the invention in an amount of 20 to 99, preferably contain 40 to 95 wt .-%.

1 to 80, preferably 5 to 60 wt .-% of the invention Molding compounds are a rubber with a glass transition temperature below -30 ° C. Suitable rubbers are, for example Styrene-butadiene rubbers, silicone rubbers, ethylene-propylene rubbers (EPM) or ethylene-propylene-diene rubbers (EPDM). EPM and EPDM rubbers can also contain up to 40% polyethylene. 1,4-Hexadiene, norbornadiene or Cyclopentadiene in an amount up to 10 wt .-%, based on the total amount of rubber.

The composition of ethylene and propylene is not limited, as long as a glass transition temperature of the amorphous component of less than -30 ° C is reached.

A typical composition for commercially available EPM rubber is, for example, 10-60% propylene units and 90-40 wt% ethylene units. There are no ethylene units 0-40% by weight on a pure polyethylene component, the rest together with the propylene forms the copolymer part.  

EPDM rubbers are composed accordingly, in In addition to propylene and ethylene, copolymers are also present still 1-10% by weight of a diene from the above-mentioned Type built in. The melt viscosity of typical EPM and EPDM rubber is between 3 and 300 g / 10 min (MFI 230/5).

The Mooney viscosity (measured at 121 ° C, ML) is typically between 20 and 80. The yield stress at 60% Elongation is typically 10-300 psi (pound / sq inch; 1 psi = 6894.8 kg / m · s² or Pa).

Typical rubbers that can be used are, for example, under the current trade name Vistalon, Exxelor (Exxon Chemicals), Dutral (Dutral S.A.), Nordel [duPont) or Buna (Veba) on the market.

Except for the syndiotactic propylene polymer and the Rubber can still the molding composition of the invention Contain usual additives, for example Stabilizers, antioxidants, UV absorbers, Light stabilizers, metal deactivators, radical scavengers, Fillers and reinforcing agents, plasticizers, Lubricants, emulsifiers, pigments, optical brighteners, Flame retardants, antistatic agents, blowing agents.

The molding composition according to the invention can be produced according to that in plastics processing for mixing Polymers and additives are customary methods.

One way is sintering in a high-speed Mixer if all components of the molding compound are in powder form are.

Another option is to use an extruder with mixing and kneading elements on the screw.

Finally, there are also kneaders like those in the rubber and Rubber industry are used, suitable Mixing machines.  

The mixing temperature depends on the respective Composition of the molding compound.

The molding composition according to the invention is characterized by low Hardness in combination with high impact strength, even with Temperatures below 0 ° C. Generally this is molding compound can be used wherever rubber-elastic behavior in Combination with high impact strength is desired.

It is suitable, for example, as a replacement for soft PVC. In automotive engineering, for example, Spoilers, seals, fender linings, Tractor fenders, trim parts or Sound insulation layers can be used.

In the construction sector it is for seals, vapor barriers or Flat roof foils and insulating jackets for pipes suitable.

Foam extrusion gives elastic, highly insulating Sheathing and coverings.

The molding composition according to the invention is also suitable for Manufacture of heavy goods bags and sealing foils, as well as Sealing membranes for landfills.

The following examples are intended to illustrate the invention explain.

SI = syndiotaxy index (by 13 C-NMR spectroscopy).
n _syn = mean syndiotactic chain length (by 13 C-NMR).
n _PE = medium block length polyethylene.
n _PP = Average block length polypropylene.
VZ = viscosity number measured at 135 ° C as a 0.1% solution in decahydronaphthalene in a capillary viscometer.
MFI 230/5 = melt index at 230 ° C, 5 kg load, according to DIN 53 735.
M _w / M _n = polydispersity.
KDH = ball indentation hardness (based on DIN 53 456, 4 mm thick plates, 240 ° C injection temperature).
a _ns = impact strength according to DIN 53 753-V-0.1, standard small bar (50 × 6 × 4 mm).
BEM = bending modulus of elasticity according to DIN 53 457 (injection molded specimens 80 × 10 × 4 mm).

A was used for the production of the molding compounds Twin screw extruder ZSK 28 (Werner & Pfleiderer) used.

example 1

A molding composition was produced by extrusion from 80 wt .-% syndiotactic polypropylene, based on the total molding composition, and 20 wt .-% of a rubber following Composition: 37% by weight propylene units and 63% by weight Ethylene units; Was 20 wt .-% of the rubber composition Polyethylene and 80 wt .-% an ethylene-propylene copolymer (EMP) consisting of 46% propylene units and 54% by weight Ethylene units. The MFI 230/5 was 11 g / 10 min VZ 284 cm³ / g.

The syndiotactic polypropylene used had an SI of 94.5%, an n _syn of 32 and an MFI 230/5 of 266 g / 10 min, corresponding to a VZ of 97 cm³ / g.

The following were determined as mechanical data: KDH = 45 Nmm ^-2 ; BEM = 792 Nmm ^-2 ; a _ns = 5.8 mJmm ^-2 (23 ° C), 1.9 mJmm ^-2 (-20 ° C).

8 kg of the syndiotactic polypropylene powder were mixed with 2 kg of the rubber mixed and the mixture with 10 g Pentaerythrityl tetrakis [3 (3,5-di-t-butyl-4-hydroxyphenyl) propionate-] against chemical degradation under Extrusion conditions stabilized. In the five heating zones of the extruder were 100 ° C (feed), 170 ° C, 200 ° C, 200 ° C and set at 190 ° C (nozzle plate).  

The extruder screw was operated at 100 rpm; the melt temperature of the mixture in the extruder was 210 ° C. The following data were measured on the molding composition produced in this way: MFI 230/5 = 148 g / 10 min; VZ = 123 cm³ / g; KDH = 32 Nmm ^-2 ; BEM = 694 Nmm ^-2 ; a _ns = 13.8 mJmm ^-2 (23 ° C), 5.9 mJmm ^-2 (-20 ° C).

Comparative Example A

Under the same conditions as in Example 1, isotactic polypropylene was used instead of the syndiotactic polypropylene, which had an MFI 230/5 of 169 g / 10 min corresponding to a VZ of 128 cm³ / g. The molding composition thus obtained had the following data: MFI 230/5 = 100 g / 10 min; VZ = 150 cm³ / g; KDH = 68 Nmm ^-2 ; BEM = 1380 Nmm ^-2 ; a _ns = 6.8 mJmm ^-2 (23 ° C), 3.5 mJmm ^-2 (-20 ° C).

The result of the comparative example shows that with isotactic polypropylene instead of syndiotactic Polypropylene neither the desired low hardness nor the high impact strength can be achieved.

Example 2

Example 1 was repeated; however, a syndiotactic polypropylene with an SI of 93.8%, an n _syn and 25 and an MFI 230/5 of 153 cm³ / g was used as the syndiotactic component.

The mechanical data of this polymer were determined: KDH = 40 Nmm ^-2 ; BEM = 604 Nmm ^-2 and a _ns = 17.5 mJmm ^-2 (23 ° C), 2.8 mJmm ^-2 (-20 ° C).

In the five heating zones of the extruder, 110 ° C (feed), 190 ° C, 230 ° C, 230 ° C and 200 ° C (nozzle plate) set. The extruder screw was operated at 40 rpm. The melt temperature of the mixture in the extruder was 250 ° C.  

The following data were measured on the molding compound prepared in this way: MFI 230/5 = 19 g / 10 min; VZ = 147 cm³ / g; KDH = 27 Nmm ^-2 ; BEM = 555 Nmm ^-2 ; a _ns = 35.9 mJmm ^-2 (23 ° C), 9.4 mJmm ^-2 (0 ° C), 6.9 mJmm ^-2 (-20 ° C).

 Comparative Example B

Under conditions comparable to Example 2, isotactic polypropylene was used instead of the syndiotactic polypropylene, which had the following values: MFI 230/5 = 13 g / 10 min corresponding to a VZ of 258 cm³ / g. The molding composition thus obtained showed the following data: MFI 230/5 = 15 g / 10 min; VZ = 250 cm³ / g; KDH = 52 Nmm ^-2 ; BEM = 1052 Nmm ^-2 ; a _ns = 16.3 mJmm ^-2 (23 ° C), 7.7 mJmm ^-2 (0 ° C), 5.3 mJmm ^-2 (-20 ° C).

The result shows that with isotactic polypropylene instead of syndiotactic, neither the desired low hardness (KDH, BEM) nor the high impact strength (a _ns ) can be achieved.

Example 3

Example 2 was repeated, a syndiotactic polypropylene with an SI of 94.8%, an n _syn of 29 and an MFI 230/5 of 0.7 cm³ / g corresponding to a VZ of 317 cm³ / g was used as the syndiotactic component.

The mechanical data of this polymer were determined: KDH = 36 Nmm ^-2 ; BEM = 527 Nmm ^-2 and a _ns = 46.6 mJmm ^-2 (23 ° C), 7.8 mJmm ^-2 (-20 ° C).

In the five heating zones of the extruder, 180 ° C (feed), 230 ° C, 280 ° C, 280 ° C and 275 ° C (nozzle plate) set. The extruder screw was operated at 35 rpm.

The melt temperature of the mixture in the extruder was 300 ° C. The following data were measured on the molding compound prepared in this way: MFI 230/5 = 1.3 g / 10 min; VZ = 308 cm³ / g; KDH = 20 Nmm ^-2 ; BEM = 400 Nmm ^-2 ; a _ns = 53.4 mJmm ^-2 and partly without break (23 ° C), 23.2 mJmm ^-2 (0 ° C), 10.0 mJmm ^-2 (-20 ° C).

Examples 4, 5 and 6

Example 2 was repeated, the ones used However, rubber amounts were 5% (example 4), 10% (Example 5) and 40% (Example 6), each based on the entire molding compound.

The results:

Example 7

Example 2 was repeated as a syndiotactic component however, became a syndiotactic ethylene / propylene copolymer used with the following properties:

Average polypropylene block length (n _PP ) = 26, average polyethylene block length (n _PE ) = approx. 1, M _w / M _n = 2.2, SI = 97.2%, VZ = 149 cm³ / g, copolymerized ethylene content = 2.5% by weight.

In addition, only 10% rubber was used instead of 20%, based on the total polymer mass. The blend described here showed the following data:
MFI 230/5 = 26 g / 10 min; VZ = 150 cm² / g; KDH = 17 Nmm ^-2 ; a _ns = 40.4 mJmm ^-2 (23 ° C), 12.6 mJmm ^-2 (0 ° C), 7.3 mJmm ^-2 (-20 ° C).

Example 8

The procedure was as in Example 7, as a syndiotactic However, the component became a two-stage polymerized syndiotactic block copolymer used (1st stage: syndiotactic polypropylene, 2nd stage: ethylene / propylene copolymer).

The syndiotaxy index of the polypropylene portion (77.5% by weight based on the total amount of the block copolymer) was 96.4%; there was a VZ of 275 cm³ / g. The 22.5% by weight of the entire block copolymer ethylene / propylene copolymer consisted of 22.1% by weight of ethylene units, the remaining 77.9% by weight of syndiotactically linked propylene units. The VZ was 304 cm³ / g, the ethylene was 40.5% isolated (n _PE = 1), 10.5% with n _PE = 2 and 49.0% installed in blocks (n _PE 3).

The following data were measured on the molding composition produced in this way:
MFI 230/5 = 8 g / 10 min; VZ = 260 cm³ / g; KDH = 13 Nmm ^-2 ; a _ns = without break at 23 ° C, 24.7 mJmm ^-2 (0 ° C), 10.0 mJmm ^-2 (-20 ° C).

Comparative Example C

Under comparable conditions as in Example 3, isotactic polypropylene was used instead of the syndiotactic polypropylene, which had a melt index of 1.1 g / 10 min corresponding to a VZ of 451 cm³ / g. The molding composition obtained in this way showed the following data:
MFI 230/5 = 2.3 g / 10 min; VZ = 360 cm³ / g; KDH = 47 Nmm ^-2 ; BEM = 1151 Nmm ^-2 ; a _ns = 32.7 mJmm ^-2 (23 ° C), 9.8 mJmm ^-2 (0 ° C), 4.3 mJmm ^-2 (-20 ° C).

The result of the comparative example shows that with isotactic polypropylene instead of syndiotactic polypropylene, neither the desired low hardness (KDH, BEM) nor the high impact strength (a _ns ) can be achieved.

Claims (6)

1. polypropylene molding composition, consisting essentially of 20 to 99 wt .-%, based on the molding compound, one syndiotactic propylene polymer and 1 to 80% by weight, based on the molding compound, a rubber with a Glass temperature below -30 ° C. 2. Molding composition according to claim 1, characterized in that the syndiotactic propylene polymer is a polypropylene with a syndiotaxy index of at least 75%. 3. Molding composition according to claim 1, characterized in that the syndiotactic propylene polymer is a copolymer which contains 99.5 to 50% by weight of propylene units with a syndiotaxy index of at least 75% and 0.5 to 50% by weight. from units of ethylene or an olefin having at least 4 C atoms of the formula Ra-CH = CH-R ^b , in which Ra and R ^{b are} identical or different and denote a hydrogen atom or an alkyl radical having 1 to 10 C atoms or Ra and R ^b with the carbon atoms connecting them form a ring with 4 to 22 carbon atoms. 4. Molding composition according to claim 1, characterized in that the syndiotactic propylene polymer is a mixture of 20 to 99 wt .-% of a copolymer (a) and 1 to 80 wt .-% of a copolymer (b), wherein copolymer (a) 95 to 100 wt .-% propylene units with a syndiotaxie index of at least 75% and 0 to 5 wt .-% units of ethylene or an olefin with at least 4 carbon atoms of the formula Ra-CH = CH-R ^b , wherein Ra and R ^{b have} the abovementioned meaning, and copolymer (b) consists of 20 to 90% by weight of propylene units with a syndiotaxy index of at least 75% and 10 to 80% by weight of units of ethylene or an olefin with at least 4 carbon atoms of the formula Ra-CH = CH-R ^b , in which Ra and R ^{b have} the abovementioned meaning. 5. Molding composition according to claim 1, characterized in that they also have stabilizers, antioxidants, UV absorbers, light stabilizers, metal deactivators, Radical scavenger, filler and reinforcing agent, Plasticizers, lubricants, emulsifiers, pigments, optical brighteners, flame retardants, antistatic agents or Contains blowing agents. 6. Use of the polypropylene molding composition according to claim 1 for the production of moldings with low hardness, rubber-elastic behavior and high impact strength.